Low-voltage defrosting device



Oct. 7, 1947. HENRIQUEZ 2,428,667

LOW VOLTAGE DEFROSTING DEVICE Filed Feb. 14, 1941 0 m donafqy I!" it 5 Inventor A tiomey Patented Oct. 7, 1947 UN lT-ED STATES PATENT OFFICE LOW-VOLTAGE DEFROSTING DEVICE Robert E. He'nriquez, Monroe,'Wis.

Application February 14,1941, Serial No. 378,995

1 Claim.

My invention relates to improvements in low voltage defrosting devices for electrical refrigerator systems of the evaporation type, and is not intended for domestic refrigeration. The primary object of my invention is to provide a substantially automatically operating arrangement of this character which is adapted to establish a low voltage defrosting circuit upon completion of the refrigeration cycle, and which will automatically eliminate frost from the evaporator even though a below freezing temperature prevails therein at the start of the defrosting cycle.

Other important objects and advantages of my invention will be apparent from a reading of the following description taken in connection with the appended drawing, wherein for purposes of illustration there is shown a preferred embodiment of my invention.

In the drawing:

Figure 1 is a general schematic diagram of the device showing the components of the present invention and the electrical and mechanical con nections involved at the beginning of a defrosting period.

Figure 2 is a fragmentary enlarged vertical longitudinal sectional view taken through one of the insulated joints.

Figure 3 is an elevation of a dual contactor mercury tube.

Referring in detail to the drawings, the numeral 5 generally designates a refrigerator having a freezing compartment 6 in which are located the coils I of the evaporator, and the expansion valve 8 as well as part of the capillary tube with the bulb-9 of the temperature controlled mercury switch 9. The switch 9 is of a conventional type in which the effective element consists of a sealed tube ofinsulating material such as glass, containing a small quantityof mercury, into which contacts project. The tube is mounted in such a way on a, pivot or pivots that it may be tilted and may remain in a tilted position in either direction, in accordance with the portion of the cycle of operation of the refrigerator.

The numeral I generally designates the receiver of the condensing unit from which rises the condenser coil II which is connected to the discharge of the compresser 12 which is driven by the electric motor I3, with the intake of the compressor l2 connected by the suction line [4 to the evaporator coils I.

The liquid pipe line I is connected to the receiver Ill and through the expansion valve 8 to the inlet of the evaporator coil 1. One side of the electric motor li-3eis connected by the wire I6 to one wire I! of the A. C. supply line, while the remaining side of the motor is connected by a wire I8 to the contact point l8 at one end of the tiltable mercury tube 26 of switch 9, the tiltm being controlled by the bulb 9'. The contact point 20 at the opposite end of the tiltable mercury tube'26 of the switch 9 is connected by the wire 20 to one end of the primary 2| of the low voltage transformer which is generally designated by 22. The other end of the primary 2| is connected by wire 40 through the points 40' and 23' and wire 23 of the thermoswitch 31 to the said wire I! of the A. C. power supply line. The opposite wire 24 of the power supply is connected by a wire 25 with the contact 25' of mercury tube 26 of the switch 9.

The secondary 21 of the low voltage transformer 22 has one end thereof connected by the wire 28 to the suction end of the evaporator coil 1 here shown on the right side of the insulated joint 29, while the other end of the secondary winding 21 of the transformer 22 is connected by the wire 30 with the opposite end of the evaporator coil 1 adjacent the insulated joint 3|, whereby the passage of current through the evaporator coil 1 located between the two insulation joints 29 and 3| on the piping will be able to heat the coil 1.

The second mercury switch, which is automatic, may be substantially similar to the switch 9 and is generally designated by reference numeral 31 has its thermal bulb 38 adjacent to the evaporator coil 1. The tiltable tube 39 of the mercury switch 3'lrhas its two contacts 23' and 4'0 located at its right-hand end, as seen in Fig. 1, instead of at opposite ends, as is the case in tube 26 of the switch 9. The portion 23 of the wire I! of the power source is connected to one of these tube contacts 23', while the remaining contact 40' is connected by the wire 40 with one end of the primary winding 2| of the transformer 22.

The insulated joints 29 and 3| are both alike and are shown in detail in Figure 2 of the drawings. The pipes'are provided with the usual flanges 32 and 33 and with the usual bolts 34 passing through these flanges and clamping the same against opposite sides of a dielectric annulus 35. In addition to these provisions, insulating sleeves 36 are provided to surround the bolts 34 and to prevent their electrical engagement with either of the flanges or with the annulus 35, so that the pipes 14 and IS, in the arrangement shown in Figure 1 of the drawings, are insulated from the coil section I. The coil 1 is insulated from thebody of the refrigerator to prevent grounding of the electric circuit.

The above described, is a complete defrosting arrangement for refrigeration evaporators, using low voltage for commercial but not for domestic refrigerators, wherein the control is of the double-acting type so that, after the refrigeration cycle has taken place, the control mercury tube 26 of switch 9 has to be tilted back to its original position and complete the low voltage transformer circuit, thereby providing the necessary potentials across the evaporator coil 1 to raise the temperature thereof to about 32 F. A complete defrosting cycle is thus provided. By using this method of defrosting, much greater efiiciency is obtained from the evaporator because of its consequent freedom from frost. By using the foregoing device with forced convectional air units on low temperature application, it has been found possible to operate the condensing unit at a much higher back pressure whereby the efficiency of the unit is greatly increased. In the cycle of this unit no definite temperatures can be given as this must be gauged by particular application. Assuming a sharp freezer, its temperature should be maintained at about 20 below zero; in ice cream hardening cabinets, about 10 below and in ice-cream dispensing cabinets 5 below zero.

The foregoing arrangements are applicable for automatically defrosting ice cream cabinets, soda fountains, and sharp freezers. It is to be noted that this device is not intended for domestic use, but for low temperature work and that, in the case of forced convection units, the present invention can be applied for completely defrosting the evaporator durin the off-cycle when it is below freezing temperatures.

Referring to Figure 1 of the drawings and assuming that a refrigerator on-cycle has just bee completed, then the thermoswitch 31 with mercury tube 39 will be in the position as seen in Fig. 1, due to the fact that the thermo-bulb 38,

which is adjacent to the evaporator 1, is cold and also to the fact that the temperature control mercury tube 26 of switch 9 is then held in the one compressor operating cycle to the'beginning of the next one and it is not necessary to manipulate one or more switches to defrost the evaporator. The device is applicable to all low temperature evaporators, and more especially to the type using forced air units.

The mercury tube 39 actuated automatically by the thermostat-bulb 38 works in opposition to the tube 26 of switch 9, accordingly, tube 39 of automatic switch 31 opens the circuit when the temperature is rising, that is after the predet'ermined defrosting temperature has been reached.

Although I have shown and described herein a preferred embodiment of my invention, it is to be definitely understood that I do not desire to limit the application of my invention thereto, except as may be required by the scope of the subjoined claim,

Having described v the claimed as new is; I I i,

In combination, a refrigerating device for a temperaturebetweenfl and minus 20 C., consisting of a vaporizing device having its terminals electrically insulated and including an evaporainvention, what tor coil and an expansion valve connected to said coil, a compartment in which said evaporator coil and expansion valve are located, and exteriorly to said compartment an electric power supply, a compressor, an electric motor having one side connected to' one wire in the circuit of said power supply, a condenser having a condenser coil connected at one end with the discharge side of said compressor, atreceiver con nected with the other end of said condenser coil, 1

a suction pipe connecting one of said insulated terminals with the intake side of said compressor,

and an outlet pipe from said receiver connecting with the-vaporizing device at the other insulating terminal of said vaporizing device, a step down low voltage transformer havingthe terminalsof its secondary connected one/to each ofsaid inposition as seen in Fig. 1, that is the Wires 25 and I8 make a complete circuit to the compressor motor l3. With the switches so set the device is now put in operation by closing the power line switch (not shown) to the motor, when the mercury tube 26 of switch 9 will keep the power line circuit closed until the predetermined tem:

perature of the cooling compartmentB has been mercury tube 26 tilts in the opposite direction and thereby completes a circuit including the wires 24 and 25, 25, 20' and through wires 20,

40 to the tube 39 of switch 31. Owing to the fact that the evaporator coil 1 has been cooled to a point below freezing temperature, the thermostatic switch 31 then turns the mercury tube 39 into closed position and said tube 39 remains in that position until the temperature of the through the wire 40 of the other'side of the power pp y.

The present defrosting device is fully automatic in every respect. There will be no accumulation of frost remaining over from the end of reached. Upon reaching this temperature the f sulated terminals thereby'to heat said vaporizing device between its terminals, a thermo control switch including a. tiltable mercury tube having a thermo-bulb located within said compartment and governing the tilting of said tube, said tube having two end contacts and a central contact alternately connected with one of the end contacts or the other according to the tilted position of said tube, one of said end contacts having wire connection 'with the other side of saidmotor and the other end contact havingwire connection with the primary of said transformer and the central contact having wire connection with said electric power supply, a se ond thermocontrol automatic switch having a thermo" bulb REFERENCES CITED Y The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 882,224 Williams Mar. 17, i} 1,998,575 Furnas Apr, 23, 1935 

